The invention relates in general to keyboards and in particular to keyboards with elevated keys.
Referring to FIG. 1a, a conventional key structure as disclosed in U.S. Pat. No. 5,874,696 can be vertically depressed by moving a slider S in a first direction A. The conventional key structure in FIG. 1a primarily comprises a substrate B, a first rod L1, a second rod L2, an elastic dome E, a slider S and a key cap K. The first rod L1 has a first end L1 and a second end L12, and the second rod L2 has a third end L23 and a fourth end L24. The first rod L1 and the second rod L2 are pivotally connected via a hinge P. As shown in FIGS. 1a and 1b, the first and fourth ends L11 end L24 are movable and pivotally connected to the substrate B and key cap K respectively. The second and third ends L12 and L23 are pivotally connected to the key cap K and the substrate B respectively
When the slider S moves from a first position A1, as shown in FIG. 1a to second position A2, as shown in FIG. 1b, the slider S impels the first end L11 in the first direction A. The key cap K is therefore depressed from height H to height H′, and the key structure is in a depressed state. This conventional key structure is usually employed in a keyboard of a laptop computer. The keyboard can be normally used or miniaturized by shifting the slider S.
When the slider S impels the first rod L1 in first direction A, the key structure descends from the original state shown in FIG. 1a to the depressed state shown in FIG. 1b. However, it can be difficult to depress the key cap K by shifting the slider S because the key cap K inevitably exerts an upward elastic force perpendicular to the substrate B due to the compressed elastic dome E. Moreover, the key structure may be situated in the depressed state as shown in FIG. 1b for a long time, adversely decreasing the utility life of the elastic dome E from the long-term deformation.